Experimental and Numerical Investigation of Controlled, Small-Scale Motions in a Turbulent Shear Layer

Abstract : The effects of high-frequency fluidic actuation on the evolution of small- and large-scale motions in a turbulent shear layer downstream of a backward-facing step are investigated experimentally and numerically. The flow behind the step is characterized in the spatial and spectral domain by high-resolution diagnostic tools. Model stability problems with increasing complexity mimic the experimental setup and actuations and describe local and global flow behaviour. It is demonstrated that dissipative, high-frequency actuation effects the shear layer evolution through three domains: I - a localized dissipative, small scales domain having enhanced turbulent kinetic energy production and dissipation rate, II - a stabilized domain marked by concomitant suppression of turbulent kinetic energy production and dissipation rate, and III - a domain of re-emerging inviscid instability at lower natural frequencies and larger scales.

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